I was wondering what the text of Nagarjuna is called where he calls the Pure Land path the "easy path"

Also does this text contain the real words of Nagarjuna or did someone else write them and attributed them to him?

In the Commentary to the Ten Stages Sutra (十住毘婆沙論 = Dasabhumika-vibhasa-sastra), in Chapter 9: "Path of Ease", 易行品第九. If I may borrow some translation from Ven Dharmamitra:

...Question: This avaivartika (irreversible) bodhisattva’s initial endeavors being such as previously discussed, one [desiring to] reach the ground of the Avaivartika would have to practice all manner of difficult practices for a long time and only then be able to achieve it. He might be prone to fall down onto the ground of the Hearers. If that were the case, then this would be for him a great degenerative calamity....Therefore, if the Buddhas have, as a skillful means, mentioned the existence of an easily-practiced path by which one might rapidly succeed in arriving at the ground of the Avaivartika, then I pray that you will explain it for me....

Now, the practice itself is not "Pureland" in the sense of what is called "Pureland" nowadays. But it does focus on reciting the names of the Buddhas of the ten directions.

"Real words of Nagarjuna" - how would we know? We barely even know who Nagarjuna was in the first place! Usually we do a definition like this: "Whoever wrote the Mulamadhyamaka-karika is Nagarjuna!"

In general, the text has been considered as authored by Nagarjuna throughout East Asia. It certainly comes from the right time period, and follows that line of thought. For instance, in describing the path above, it cites Nagarjuna's Bodhisambhara sastra.